Maintenance and Reliability Best Practices. Ramesh Gulati
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activities, should be planned and scheduled before it is executed.
FIGURE 4.2 Simple Workflow Process
Figure 4.3 illustrates the workflow and key players in the maintenance workflow process. The following are the key players in this process:
• Coordinator—asset/resource
• Planner
• Scheduler
• Configuration specialist/systems engineer
• Craft supervisor
• Work performer
FIGURE 4.3 Workflow with Role Process
In addition, other players,such as maintenance/systems engineers and MRO/material personnel, play supportive roles in the workflow process.
Initially, the required or requested work task gets routed to an asset/resource coordinator. This person represents the asset owner and may work for maintenance or operations. The coordinator helps to prioritize the work, ensuring required resources are in the budget, and to schedule asset outages if necessary. The coordinator forwards the work task to a planner/scheduler or directly to the craft supervisor or maintenance crew, depending on the task’s priority and planning needs. For example, PM-type work, which should already be planned, could go directly to the maintenance scheduler. The coordinator may also work with the maintenance engineer or configuration management personnel for any technical help or if a configuration change request is needed.
As the work order gets routed from one stage to another, a WO status is assigned based on what’s being done to that WO. Figure 4.4 is a suggested list of work order status codes. In addition, work type,as suggested in Figure 4.5, is also assigned by the coordinator or the planner/scheduler. It is a good practice to code the work orders to help analyze the data for improvements. More will be said about work order classification in the next section.
Maintenance planners plan the job and create a work plan or job package that consists of what work needs to be done; how it will be done; what materials, tools, or special equipment is needed; estimated time; and skills required. The planners need to identify long delivery items and work with stores and purchasing personnel to ensure timely delivery. Planners may need to work with maintenance/systems engineers and craft supervisors for technical support to ensure that the work plan is feasible with sufficient technical details.
Maintenance schedulers—in working with the craft supervisor,coordinator, and other support staff—develop weekly, monthly, and rolling annual long-range plans to execute maintenance work. They are more concerned with when the job should be executed in order to optimize the available resources with the work at hand.
FIGURE 4.4 Work Order Status Codes
FIGURE 4.5 Work-Type Category Codes
Craft supervisors take the weekly schedule and assign who will do the job on a daily basis. In addition, they review work plans from an execution point of view and recommend necessary changes in work plans to the planner and the scheduler. It is also their responsibility to ensure that the high work quality is maintained and details of work completed are documented properly in the system.
Figure 4.6 illustrates a workflow process with its key elements;it includes an example of a productivity report based on delay hours reported and a work-estimating subprocess within the planning process utilizing the maintenance standards database.
Work Classification and Prioritization
Maintenance Work Task Classifications
Maintenance work tasks can be classified into the following categories as discussed in Chapter 3:
Preventive Maintenance (PM)
• Time (calendar)-based maintenance (TBM), age related
• Run-based maintenance (RBM), usage related
• Condition-based maintenance (CBM, aka predictive), health related
• Operator-based maintenance (OBM, aka autonomous maintenance, a pillar of TPM), operations related
Corrective Maintenance (CM)
• CM—routine work resulting from PMs, planned and scheduled
• CM—major repairs/projects, planned and scheduled
• CM—reactive, unplanned/unscheduled (aka breakdown/ emergency)
In this chapter, we explore each of these further.
FIGURE 4.6 Workflow Process
Preventive Maintenance
Preventive maintenance refers to a series of actions that are performed on an asset on schedule. That schedule may be either calendar time–based or machine operations–dependent (i.e., runtime or the number of machine cycles). These actions are designed to detect, preclude, or mitigate the degradation of a system and its components. PM includes cleaning, adjusting, and lubricating, as well as minor component replacement, to extend the life of assets and facilities. The goal of a preventive maintenance approach is to minimize system and component degradation and thus sustain or extend the useful life of the asset. Assets within your facilities should not be allowed to run to the breaking point unless a run-to-failure strategy has been selected for that specific asset. The PM work can be further classified into these categories:
PM: Time (Calendar)-Based
Time (calendar)-based maintenance is typically performed on selected calendar time. Maintenance personnel schedules periodic visits to an asset based on fixed time intervals, for example, every 3 or 6 months. Although better than no PM at all, calendar-based PMs are not the optimal way to run PM programs. They may result in too much time being spent on an asset. Numerous visits to assets with “no data—no abnormalities found” can be regarded as wasted maintenance dollars. If this happens, the PM time frame should be reevaluated and adjusted. Nevertheless, time-based PMs are a good approach for assets having a fixed operating schedule such as a 24/7 or 80 hours/week operation.
PM: Run-Based
Run-based maintenance is typically the next step up from calendar-based maintenance. It involves performing PMs based on asset cycles or runtime. Intuitively, this approach makes sense. An asset does not have to have PM if it has not been used. Generally speaking, for some failure modes, it is the actual operation of the asset that wears it down, so it makes sense to check the asset after it has been working for a specified amount of time to cause some wear. It may be necessary to either adjust or replace the component.
Condition-Based Maintenance
Condition-based maintenance, also known as predictive maintenance (PdM), attempts to evaluate the condition of an asset by performing periodic or continuous asset monitoring. This approach is the next level up from runtime-based maintenance. The ultimate goal of CBM is to perform maintenance at a scheduled time when the maintenance activity is most cost-effective, yet before the asset fails in service. The “predictive”component stems from the goal of predicting the future trend of the asset’s condition. This approach uses principles of statistical process control